1. Field of the Invention
The present invention relates generally to steering systems for marine propulsion systems and, more particularly, to a steering system which allows two or more marine propulsion devices to be selectively locked in synchrony with each other or, alternatively, be allowed to rotate about their respective steering axes independently from each other.
2. Description of the Related Art
Skilled artisans in the field of marine propulsion devices are familiar with many different types of steering apparatus which are provided for the purpose of causing marine propulsion devices to rotate about steering axes relative to a marine vessel to which they are attached. In some applications, two or more marine propulsion devices are locked to each other so that they rotate in synchrony about their respective axes. In some applications, these steering links can be deactivated to allow auxiliary marine propulsion devices to be independently trimmed or tilted out of the water and, when this condition persists, to be unlinked from a main propulsion device.
U.S. Pat. No. 3,658,027, which issued to Sturges on Apr. 25, 1972, describes a single cylinder hydraulic stabilizer for steering. It serves to lock a steering element in its position at any time valve-actuating rods of the device are not being caused to move as a result of steering forces applied thereto. The valve controls the flow of hydraulic fluid from one end of the hydraulic cylinder to the other end of the cylinder so as to permit movement of the valve block itself with respect to a portion of a vehicle, such as a boat.
U.S. Pat. No. 4,227,481, which issued Cox et al. on Oct. 14, 1980, describes a safety steering system for outboard motors. The system controls torque rotation for boats having directable marine outboard motors capable of pivoting about a vertical axis. An arm extending from the motor is connected to a flexible cable having two ends, a first end connected to a steering device and a second end connected to the arm. An actuator control valve interposed along the flexible cable is capable of locking the arm in a single position when no force from the cable is being exerted on the arm.
U.S. Pat. No. 4,266,497, which issued to Toda et al. on May 12, 1981, describes a marine steering arrangement which includes a hydraulic steering machine, variable discharge-type pump units for actuating the hydraulic steering machine and power units for remotely manipulating the pump units. The power units are provided respectively in at least two channels which include a spare channel.
U.S. Pat. No. 4,362,117, which issued to Mishina on Dec. 7, 1982, describes a marine steering gear with emergency steering means. A marine steering gear is equipped with an emergency steering means which comprises an emergency directional control valve capable of replenishing hydraulic fluid or oil to a plurality of pressure chambers of an actuator for a hydraulic steering engine through check valves and stop valves, and a relief valve designed to set a desired charge pressure and installed in lines of oil to be supplied through the directional control valve, check valves, and stop valves so as to forcibly reduce the air volumes in the pressure chambers and thereby hold the rudder blades substantially in a hydraulically locked state.
U.S. Pat. No. 4,431,422, which issued to Hall on Feb. 14, 1984, describes a marine hydraulic steering system control unit for a marine installation. It comprises a helm station including a pump comprising first and second pump discharge ports, which pump is selectively and alternatively operable to deliver fluid under pressure from the first and second pump discharge ports.
U.S. Pat. No. 4,578,039, which issued to Hall on Mar. 25, 1986, describes a marine hydraulic steering system control for a marine installation comprising a helm station including a pump comprising first and second pump discharge ports.
U.S. Pat. No. 6,406,340, which issued to Fetchko et al. on Jun. 18, 2002, describes a twin outboard motor hydraulic steering system. The assembly applies a force to tiller arms of twin marine outboard propulsion units and rotates the propulsion units about a steering axis between a center position and hard over positions to each side of the center position. A tie bar is pivotally connected to the steering apparatus and pivotally connected to the tiller arm of a second propulsion unit. The tie bar may be pivotally connected to the steering apparatus by a ball joint connected to the steering apparatus by a bracket which moves with the member.
U.S. Pat. No. 6,913,497, which issued to Ahlswede et al. on Jul. 5, 2005, discloses a tandem connection system for two or more marine propulsion devices. The connection system is intended for connecting two or more marine propulsion devices together and provides a coupler that can be rotated in place, without detachment from other components, to adjust the distances between the tie bar arms. In addition, the use of various clevis ends and pairs of attachment plates on the components significantly reduces the possibility of creating moments when forces and their reactions occur between the various components.
U.S. patent application Ser. No. 10/873,086 (M09811), which was filed by Lokken et al. on Jun. 21, 2004, discloses a connection device for a marine propulsion system. A selective locking mechanism automatically connects or disconnects two components of the marine propulsion system together in response to rotation of a tube and a rod. This relative rotation of the tube and rod is caused automatically when one of the components of the marine propulsion system is rotated relative to the other component.
U.S. patent application Ser. No. 11/248,483 (M09993), which was filed on Oct. 12, 2005 by Bradley et al., discloses a method for positioning a marine vessel. The vessel positioning system maneuvers a marine vessel in such a way that the vessel maintains its global position and heading in accordance with a desired position and heading selected by the operator of the marine vessel. When used in conjunction with a joystick, the operator of the marine vessel can place the system in a station keeping enabled mode and the system then maintains the desired position obtained upon the initial change of the joystick from an active mode to an inactive mode. In this way, the operator can selectively maneuver the marine vessel manually and, when the joystick is released, the vessel will maintain the position in which it was at the instant the operator stopped maneuvering it with the joystick.
U.S. patent application Ser. No. 11/248,482 (M09992), which was filed by Bradley et al. on Oct. 12, 2005, discloses a method for maneuvering a marine vessel in response to a manually operable control device. A marine vessel is maneuvered by independently rotating first and second marine propulsion devices about their respective steering axes in response to commands received from a manually operable control device, such as a joystick. The marine propulsion devices are aligned with their thrust vectors intersecting at a point on a centerline of the marine vessel and, when no rotational movement is commanded, at the center of gravity of the marine vessel. The internal combustion engines are provided to drive the marine propulsion devices. The steering axes of the two marine propulsion devices are generally vertical and parallel to each other. The two steering axes extend through a bottom surface of the hull of the marine vessel.
U.S. Pat. No. 5,755,605, which issued to Äsberg on May 26, 1998, describes a propeller drive unit. Installation in a boat has two propeller drive units which extend out through individual openings in the bottom of a V-bottomed boat, so that the legs are inclined relative to each other. The leg of one drive unit can be set to turn the boat in one direction at the same time as the leg of the other drive unit can be set to turn the boat in the opposite direction, so that the horizontal counteracting forces acting on the legs cancel each other, while the vertical forces are added to each other to trim the running position of the boat in the water.
U.S. Pat. No. 6,234,853, which issued to Lanyi et al. on May 22, 2001, discloses a simplified docking method and apparatus for a multiple engine marine vessel. A docking system is provided which utilizes the marine propulsion unit of a marine vessel, under the control of an engine control unit that receives command signals from a joystick or push button device, to respond to a maneuver command from the marine operator. The docking system does not require additional propulsion devices other than those normally used to operate the marine vessel under normal conditions. The docking and maneuvering system uses two marine propulsion units to respond to an operator's command signal and allows the operator to select forward or reverse commands in combination with clockwise or counterclockwise rotational commands either in combination with each other or alone.
International Patent Application WO 03/042036, which was filed by Arvidsson on Nov. 8, 2002, describes a remote control system for a vehicle. It comprises a primary heading sensor fixedly attached to the vehicle, the primary heading sensor being adapted to detect a reference heading, a remote control unit comprising a steering input manipulator, the remote control unit being either portable by a user or rotationally attached to the vehicle relative to a marine axis of the vehicle, the remote control unit being adapted to communicate steering input data to a steering computer programmed to process the steering input data into steering commands and to communicate the steering commands to a steering mechanism of the vehicle. The remote control unit comprises a secondary heading sensor which is synchronized with the primary heading sensor with respect to the reference heading, and the steering input data includes information of an active position of the steering input manipulator relative to the reference heading, the active position of the steering input manipulator determining the desired direction of travel of the vehicle regardless of the orientation of the remote control unit relative to the main axis of the vehicle.
International Patent Application WO 03/093102, which was filed by Arvidsson et al. on Apr. 29, 2003, describes a method of steering a boat with double outboard drives and a boat having double outboard drives. The method of steering a planing V-bottomed boat with double individually steerable outboard drive units with underwater housings, which extend down from the bottom of the boat, is described. When running at planing speed straight ahead, the underwater housings are set with “toe-in” (i.e. inclined toward each other with opposite angles of equal magnitude relative to the boat centerline). When turning, the inner drive unit is set with a greater steering angle than the outer drive unit.
U.S. Pat. No. 6,431,928, which issued to Aarnivuo on Aug. 13, 2002, describes an arrangement and method for turning a propulsion unit. The propeller drive arrangement includes an azimuthing propulsion unit, a power supply, a control unit, and a sensor means. An operating means is provided for turning the azimuthing propulsion unit in relation to the hull of the vessel for steering the vessel in accordance with a steering command controlled by the vessel's steering control device. The operating means also includes a second electric motor for turning the azimuthing propulsion unit via a mechanical power transmission that is connected to the second electric motor.
U.S. Pat. No. 6,623,320, which issued to Hedlund on Sep. 23, 2003, describes a drive means in a boat. A boat propeller drive with an underwater housing which is connected in a fixed manner to a boat hull and has tractor propellers arranged on that side of the housing facing ahead is described. Arranged in that end portion of the underwater housing facing astern is an exhaust discharge outlet for discharging exhaust gases from an internal combustion engine connected to the propeller drive.
U.S. Pat. No. 6,712,654, which issued to Putaansuu on Mar. 30, 2004, describes a turning of a propulsion unit. The arrangement for moving and steering a vessel includes a propulsion unit having a chamber positioned outside the vessel equipment for rotating a propeller arranged in connection with the chamber, and a shaft means connected to the chamber for supporting the chamber in a rotatable manner at the hull of the vessel. At least one hydraulic motor is used for turning the shaft means in relation to the hull of the vessel for steering the vessel. The arrangement also includes means for altering the rotational displacement of the hydraulic engine.
The patents described above are hereby expressly incorporated by reference in the description of the present invention.
When two or more marine propulsion devices are independently rotatable about their respective steering axes, it would be significantly beneficial if the marine propulsion devices could be selectively locked to each other for synchronous rotation about their axes or, alternatively, allowed to rotate independently about their individual axes in order to allow an improved degree of maneuverability of the associated marine vessel, especially when the marine vessel is being maneuvered into a docking space.